<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="./666.css">
    <style>
        h1 {
            text-align: center;
        }
    </style>
</head>

<body>
    <button>我是小牛马</button>
    <ul>
        <li>我不是小牛马</li>
    </ul>
    <h1>我是大大滴牛马</h1>
    <h2>我是牛马它的父亲</h2>
    <h2>我是牛马它的儿子</h2>
</body>

</html>